In turbine engine construction it is common to use a stator to control and direct the flow of air within the compressor of the turbine engine. Radial vanes are commonly used to direct the flow. The vanes have a blade like shape and are typically attached at one end to an external housing and can be attached at the other end to an internal hub. The vanes generally have a radial orientation. Variable vanes include a control mechanism that rotates the vanes about their radial axis to control the direction and amount of airflow into downstream parts of the engine.
Variable geometry or static guide vanes, especially those having a locating button on the unshafted end, normally require a split ring housing, a separate locating ring, axial clearance grooves or a combination of these features in order to assemble the vane pattern. The requirement for these assembly methods in prior art devices is based on the fact that some form of axial motion is required to assemble the vanes into their final position caged inside the engine. All three methods have disadvantages. Using a split ring housing increases manufacturing costs because the two rings must be machined and maintained as a matched set. Making a separate locating ring requires making an additional, often flimsy part that can be difficult to hold in place and has holes with close tolerances making it expensive. Using axial clearance grooves creates a distortion pattern on the flow path that is aerodynamically undesirable.
Various attempts have been made to overcome these limitations of the prior art. U.S. Pat. No. 5,328,327 discloses a method of installing a set of vanes that does not use any of the prior described methods but that does require threaded members 72 to hold the vanes into the housing ring. These threaded members require a complex installation method and because the vanes are designed to pivot, the threaded members pose a risk of becoming loose.
As can be seen, there is a need for an improved variable geometry vane and vane installation method. There is a need for variable geometry vanes that can be easily installed in turbine engines without the need for a split ring housing or specialized machining techniques. There is a need for a variable geometry vane that can be installed and retained without the use of threaded fasteners that can become loose.